Which hash algorithm should I use?

SHA-256 for all general-purpose and security uses. SHA-512 if you need a longer output. MD5 only for legacy checksums (non-security). SHA-1 is deprecated — avoid for new implementations. The Web Crypto API supports SHA-256, SHA-384, and SHA-512 natively; MD5 requires a pure-JS implementation.

Is it safe to hash passwords or API keys online?

Only if the tool is verifiably client-side. Open DevTools → Network tab, enter your sensitive data, and confirm no network request fires. brevio Hash Generator uses crypto.subtle.digest() — a browser built-in — with zero network transmission. For comparison, server-side hash tools receive your input before hashing it.

Can you reverse a SHA-256 hash?

No. Cryptographic hashes are one-way functions: given the hash, you cannot compute the original input without trying all possible inputs (preimage attack). For short or common inputs like passwords, rainbow tables and dictionary attacks can crack weak hashes — this is why passwords should be hashed with bcrypt/argon2 (with salt) rather than plain SHA-256.

What is the difference between hashing and encryption?

Encryption is reversible with the correct key; hashing is not reversible. Encryption is used for confidentiality (protect data you want to recover). Hashing is used for integrity verification (confirm data hasn't changed) and one-way storage (passwords).

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How to Generate SHA-256 and Other Hashes Without Uploading

Last updated: 11 June 2026

You can generate SHA-256, MD5, and other cryptographic hashes entirely in your browser using brevio Hash Generator — the Web Crypto API computes hashes locally in JavaScript. No data is sent to any server.

Hashing sensitive data — passwords, API keys, private keys, confidential text — through an online tool that uploads to a server defeats the purpose. The Web Crypto API (crypto.subtle.digest()) is built into every modern browser and computes hashes indistinguishably from server-side tools, with zero network transmission.

How to Generate a Hash Without Uploading

Open brevio Hash Generator. No account required.
Select the hash algorithm. SHA-256 is the standard for most security uses. MD5 is available for legacy compatibility (not recommended for security purposes). SHA-1, SHA-384, and SHA-512 are also available.
Enter your text or paste your data. The input is processed locally — no keystrokes or content are transmitted.
Copy the hash. The hexadecimal hash string is generated in real-time as you type using crypto.subtle.digest().

How to Verify No Data Is Transmitted

Open DevTools (F12 or ⌘⌥I) → Network tab. Type or paste your sensitive data and observe. You should see zero network requests triggered by the input — only the initial static asset loads. If any fetch or XHR fires when you enter text, the tool is not client-side. This check is especially important when hashing passwords or credentials.

Which Hash Algorithm Should You Use?

Algorithm	Output Length	Security Status	When to Use
SHA-256	256 bits / 64 hex chars	Secure	General-purpose, file checksums, HMAC, TLS
SHA-512	512 bits / 128 hex chars	Secure	High-security hashing, longer output needed
SHA-384	384 bits / 96 hex chars	Secure	TLS certificates, subresource integrity
SHA-1	160 bits / 40 hex chars	Deprecated	Legacy systems only — not for new implementations
MD5	128 bits / 32 hex chars	Broken for security	Non-security checksums (file deduplication, legacy APIs)

What Hashing Is and Is Not

A hash function is a one-way transformation: given input data, it produces a fixed-length string (the digest). The same input always produces the same output; different inputs produce different outputs (with negligible collision probability for secure algorithms). Hashing is not encryption — you cannot reverse a hash to recover the original input. Use cases: verifying file integrity (compare hash before/after download), storing passwords (hash + salt, not plain hash), generating checksums for data comparison, creating fingerprints for deduplication.

Hash Generator Comparison

Tool	Upload?	Algorithms	Free?	Works Offline?
brevio Hash Generator	No — in-browser	MD5, SHA-1, SHA-256, SHA-384, SHA-512	Yes	Yes (once loaded)
CyberChef	No — in-browser (open source)	50+ algorithms	Yes	Yes (self-hostable)
md5hashgenerator.com	Yes — server upload	MD5 only	Yes	No
OpenSSL (CLI)	No — local	All standard algorithms	Free	Yes

Command Line Alternative (OpenSSL)

# SHA-256 hash of a string echo -n "your text here" | openssl dgst -sha256 # SHA-256 hash of a file openssl dgst -sha256 filename.txt

Available on macOS and Linux by default. On Windows, use Git Bash or WSL.

Frequently Asked Questions

Which hash algorithm should I use?: SHA-256 for all general-purpose and security uses. SHA-512 if you need a longer output. MD5 only for legacy checksums (non-security). SHA-1 is deprecated — avoid for new implementations. The Web Crypto API supports SHA-256, SHA-384, and SHA-512 natively; MD5 requires a pure-JS implementation.
Is it safe to hash passwords or API keys online?: Only if the tool is verifiably client-side. Open DevTools → Network tab, enter your sensitive data, and confirm no network request fires. brevio Hash Generator uses crypto.subtle.digest() — a browser built-in — with zero network transmission. For comparison, server-side hash tools receive your input before hashing it.
Can you reverse a SHA-256 hash?: No. Cryptographic hashes are one-way functions: given the hash, you cannot compute the original input without trying all possible inputs (preimage attack). For short or common inputs like passwords, rainbow tables and dictionary attacks can crack weak hashes — this is why passwords should be hashed with bcrypt/argon2 (with salt) rather than plain SHA-256.
What is the difference between hashing and encryption?: Encryption is reversible with the correct key; hashing is not reversible. Encryption is used for confidentiality (protect data you want to recover). Hashing is used for integrity verification (confirm data hasn't changed) and one-way storage (passwords).